Camm95Z28

A few weeks ago, the fuel pump on my Z died. My mechanic told me instead o fbuying the stock pump, buy a high flow one. I bought a GMS pump from Summit which flows 255 lph. I brought this up to him before ordering and he told me that the PCM will still have the system pump normal amounts of fuel and that my gas mileage should improve. Since then, I can't say it improved but has reminded me of my Dad' s 68 Z sucking down gas. Did I get bamboozled by my mechanic with the high flow pump? or do I need something else? Maybe a new fuel filter? I thank you here for your time and help.

shoebox

The PCM regulates the amount of fuel used. The pump should have no effect on mileage if you did not change anything else. It would only give you the capability of more flow if you had bigger injectors or other fuel system mods.

Injuneer

Check the fuel pressure.

There's no reason for a larger fuel pump to either improve or hurt gas mileage. As Rob points out, the PCM calculates the injector pulse width, and is totally "blind" to the fuel pump capacity or pressure. The stock fuel pressure regulator should be able to control the rail pressure of the 255LPH pump, leaving the system operation unchanged. If for some reason, your fuel pressure has been increased, it may have increased to the point where the PCM can no longer compensate for the increased flow through the injectors by using the long term fuel corrections. That would indicate a problem with the FPR or a problem with the connecting lines, not the fact that the pump capacity has increased.